The present invention relates to a new high functionality MDI. More specifically, this invention relates to an alcohol or diol based allophanate-modified MDI, which is further converted to a higher functionality allophanate product. These higher functionality allophanate products are referred to as polymeric allophanates herein. The present invention also relates to prepolymers of these polymeric allophanates, to a process of making and using the polymeric allophanates, and to a process of making and using the prepolymers of the polymeric allophanates.
Copending application, Ser. No. 10/0017,060, filed Dec. 13, 2001, which is commonly assigned, discloses a method of reducing the acidity of polymeric MDI and then treating the p-MDI with an alcohol in the presence of an allophanate catalyst to produce a dark colored allophanate-modified polymeric MDI. However, this application does not disclose a polymeric allophanate with higher functionality.
Allophanate-modified diphenylmethane diisocyanates and prepolymers thereof are known and described in, for example, U.S. Pat. Nos. 5,319,053, 5,319,054, 5,440,003, 5,663,272 and 5,686,042.
U.S. Pat. No. 5,319,053 discloses a process for preparing stable liquid allophanate-modified MDI isocyanates and prepolymers of these allophanate-modified MDI isocyanates. This process comprises reacting a specific MDI isomer composition with an aliphatic alcohol containing between 1 and 36 carbon atoms to give an allophanate-modified MDI having an NCO group content of 12 to 32.5%.
U.S. Pat. No. 5,319,054 describes a process for producing diallophanate-modified MDI by reacting the diurethane which is the reaction product of one equivalent of a diisocyanate with one equivalent of an aliphatic alcohol or an aromatic alcohol, with 4,4′-MDI containing about 2 to about 60% by weight of the 2,4-isomer of MDI. These diallophanates have NCO group contents of about 12 to about 30%.
EP 641,812 discloses the use of allophanate-modified MDI prepolymers in automotive RIM and rigid foam applications. It is a distinct feature of the invention that the flex modulus of the RIM products can be increased without modifying the chain extender composition or content.
Stable, liquid, diallophanate-modified diphenylmethane diisocyanate is known and described in, for example, U.S. Pat. No. 5,686,042. These diallophanate-modified diisocyanates are prepared from the diurethane of an alcohol and a diisocyanate and MDI. The diallophanate or a prepolymer thereof are disclosed as being used in a RIM process to produce elastomers with improved flex modulus. Since these diallophanates form elastomers with improved flex modulus, lower levels of fast reacting chain extenders are required to reach a given stiffness.
Urethane-free, allophanate-modified diphenylmethane diisocyanates are known and disclosed in, for example, U.S. Pat. No. 5,567,793. This reference also discloses the use of urethane-free, allophanate-modified isocyanates in RIM processes to improve the flex modulus of the resultant elastomers.
U.S. Pat. No. 5,663,272 discloses allophanate-modified MDI prepolymers and their use in RIM processes to improve the flex modulus of the resultant elastomers. These allophanate modified MDI's are made from a monoisocyanate with an organic compound having at least two OH groups to form a urethane, and then converting the urethane to allophanate by reacting with an isomeric mixture of MDI.
Allophanate-modified MDI's, various prepolymers thereof and other modifications thereof, can in used in various end use applications such as, for example, footwear and flexible foams, as is known and described in, for example, U.S. Pat. Nos. 5,663,272, 5,821,275 5,874,485 and 6,271,279.
Advantages of the polymeric allophanates and prepolymers thereof of the present invention include the creation of a unique high functionality molecule that can vary over a broad functionality range. These polymeric allophanates and prepolymers thereof are light in color and low in acidity and have unique curing characteristics when used in polymers.